Key facts
- If confirmed, it would mark the first confirmed detection of gaseous FeS in interstellar space, according to the paper's authors.
- The authors report a column density for FeS of ∼1.7×1015 cm−2.
- The authors caution that FeS emission may originate from a different region, just as emission from the metallic salt NaCl does.
- The results support FeS in interstellar grains and fit with grain destruction as an important source of the FeS emission, the authors say.
A team led by Aitana Tasa-Chaveli reported a tentative detection of iron sulfide gas toward Orion SrcI, the massive disk, in a preprint submitted Oct. 5, 2026, Astrobiology Web said in a report published Oct. 25, 2026.
The authors present FeS as a refractory (heat-resistant) compound seen in meteorites before offering their new detection, and they note that earlier signs of FeS showed up only in solid form within a planet-forming setting. The manuscript runs 15 pages with three figures and four tables, and The Astrophysical Journal has accepted it under the subject Astrophysics of Galaxies (astro-ph.GA).
The authors give a column density (the amount of FeS along the line of sight) for FeS at ∼1.7×1015 cm−2, derived from the same millimeter-wave spectroscopic calculations and observational report described in the preprint. The paper’s authors say confirmation would make this detection the first of its kind for gaseous FeS in interstellar space.
Past reports of FeS have stayed within solid material in a planet-forming setting, so spotting it in gas between the stars would mark a first. The authors say sulfur locked in FeS trails sulfur in SO2 and SiS by more than three orders of magnitude in their reservoir comparison, part of their review of sulfur stores in the disk they observed.
The authors warn that the FeS emission might come from another region, much like emission from the metallic salt NaCl, so the signal’s spatial origin stays uncertain compared with other tracers such as NaCl. The authors say the results back FeS in interstellar grains and agree with grain destruction as a key source of the FeS emission, tying the gas to solid material on dust grains released by destructive processes.
The authors say the observations have not yet shown if FeS is a main sulfur reservoir in molecular clouds or a leading carrier of refractory iron-bearing material, so the bigger role of FeS in massive star-forming regions stays unresolved until more data arrives. FeS draws astrobiological interest because it serves as a precursor to pyrite (FeS2), important for anaerobic metabolism, a role the authors give alongside its dust chemistry function.
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